Behavioral and related disorders are frequently reported in association with childhood epilepsy but the reasons for this are unclear. In a long-term prospective, community-based study of newly-diagnosed childhood epilepsy, behavioral assessments (Child Behavior Checklist) were performed in children 8 to 9 years after the initial diagnosis of epilepsy to determine the impact of remission and medication status on behavioral problems. Children with epilepsy were also compared with sibling controls. A total of 226 children (108 females, 118 males; mean age 13y 1mo [SD 2y 8mo], range 8-17y) with idiopathic or cryptogenic epilepsy were included in the analyses. One hundred and twenty-eight matched pairs were included in analyses of case-sibling differences. Lack of remission and current medication use were associated with worse behavioral problem and competency scores. Lack of remission generally had a greater effect than medication use, except for attention problems; medication status had the more deleterious effect (p less than 0.001). Children with epilepsy had significantly worse behavioral problems and competency scores relative to sibling controls. Even in Paris in which the patient was seizure-free and off medication, significant case-sibling differences persisted for most scales (p=0.05 to p=0.001). Lack of remission and continued use of antiepileptic drugs have a negative influence on behavioral problems in children with epilepsy but do not fully explain the worse scores relative to siblings. This suggests an independent effect associated with the epilepsy itself.